An environmental analysis extends beyond just the operating efficiency and emissions. A life-cycle assessment involves production and post-use considerations. A cradle-to-cradle design is more important than a focus on a single factor such as energy efficiency.[8][9]

Green vehicles include vehicles types that function fully or partly on alternative energy sources other than fossil fuel or less carbon intensive than gasoline or diesel.

Another option is the use of alternative fuel composition in conventional fossil fuel-based vehicles, making them function partially on renewable energy sources. Other approaches include personal rapid transit, a public transportation concept that offers automated, on-demand, non-stop transportation on a network of specially built guideways.

Hybrid electric vehicles[edit]

Hybrid cars may be partly fossil fueled and partly electric or hydrogen-powered. They are more expensive to purchase but cost redemption is achieved in a period of about 5 years due to better fuel economy.[11][12]

Solar car races are held on a regular basis in order to promote green vehicles and other "green technology". These sleek driver-only vehicles can travel long distances at highway speeds using only the electricity generated instantaneously from the sun.

Diesel-powered vehicles can often transition completely to biodiesel, though the fuel is a very strong solvent, which can occasionally damage rubber seals in vehicles built before 1994. More commonly, however, biodiesel causes problems simply because it removes all of the built-up residue in an engine, clogging filters, unless care is taken when switching from dirty fossil-fuel derived diesel to bio-diesel. It is very effective at 'de-coking' the diesel engines combustion chambers and keeping them clean. Biodiesel is the lowest emission fuel available for diesel engines. Diesel engines are the most efficient car internal combustion engines. Biodiesel is the only fuel allowed in some North American national parks because spillages will completely bio-degrade within 21 days. Biodiesel and vegetable oil fuelled, diesel engined vehicles have been declared amongst the greenest in the US Tour de Sol competition.

This presents a problem, however, as biofuels can use food resources in order to provide mechanical energy for vehicles. Many experts point to this as a reason for growing food prices, particularly US Bio-ethanol fuel production which has affected maize prices. In order to have a low environmental impact, biofuels should be made only from waste products, or from new sources - like algae.

Other[edit]

Public transportation vehicles are not usually included in the green vehicle category, but Personal rapid transit (PRT) vehicles probably should be. All vehicles that are powered from the track have the advantage of potentially being able to use any source of electric energy, including sustainable ones, rather than requiring liquid fuels. They can also switch regenerative braking energy between vehicles and the electric grid rather than requiring energy storage on the vehicles. Also, they can potentially use the entire track area for solar collectors, not just the vehicle surface. The potential PRT energy efficiency is much higher than that which traditional automobiles can attain.

Wind-powered electric vehicles primarily use wind-turbines installed at a strategic point of the vehicle, which are then converted into electric energy which causes the vehicle to propel.

Organic transit vehicles, also known as ELF bikes, go up to 20 MPH using electric power and 30 MPH with pedal power added. Most state laws classify them as bicycles.

Animal powered vehicles[edit]

Horse and carriage are just one type of animal propelled vehicle. Once a common form of transportation, they became far less common as cities grew and automobiles took their place. In dense cities, the waste produced by large numbers of transportation animals was a significant health problem. Oftentimes the food is produced for them using diesel powered tractors, and thus there is some environmental impact as a result of their use.

Human powered vehicles[edit]

Human powered transport includes walking, bicycles, velomobiles, row boats, and other environmentally friendly ways of getting around. In addition to the health benefits of the exercise provided, they are far more environmentally friendly than most other options. The only downside is the speed limitations, and how far one can travel before getting exhausted.

Benefits of green vehicle use[edit]

Environmental[edit]

Vehicle emissions contribute to the increasing concentration of gases linked to climate change.[18] In order of significance, the principal greenhouse gases associated with road transport are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).[19] Road transport is the third largest source of greenhouse gases emitted in the UK, and accounts for over 20% of total emissions,[20] and 33% in the United States.[21] Of the total greenhouse gas emissions from transport, over 85% are due to CO2 emissions from road vehicles. The transport sector is the fastest growing source of greenhouse gases.[22]

Health[edit]

Vehicle pollutants have been linked to human ill health including the incidence of respiratory and cardiopulmonary disease and lung cancer. A 1998 report estimated that up to 24,000 people die prematurely each year in the UK as a direct result of air pollution.[23] According to the World Health Organisation, up to 13,000 deaths per year among children (aged 0–4 years) across Europe are directly attributable to outdoor pollution. The organization estimates that if pollution levels were returned to within EU limits, more than 5,000 of these lives could be saved each year.

Monetary[edit]

Criticism[edit]

A study by CNW Marketing Research suggested that the extra energy cost of manufacture, shipping, disposal, and the short lives of some of these types of vehicle (particularly gas-electric hybrid vehicles) outweighs any energy savings made by their using less petroleum during their useful lifespan.[25] Critics of the report note that the study prorated all of Toyota's hybrid research-and-development costs across the relatively small number of Priuses on the road, rather than using the incremental cost of building a vehicle; used109,000 miles (175,000 km) for the length of life of a Prius (Toyota offers a 150,000-mile (240,000 km) warranty on the Prius' hybrid components, including the battery), and calculated that a majority of a car's cradle-to-grave energy gets expended during the vehicle's production, not while it is driven.[26]

Norwegian Consumer Ombudsman official Bente Øverli stated that "Cars cannot do anything good for the environment except less damage than others." Based on this opinion, Norwegian law severely restricts the use of "greenwashing" to market automobiles, strongly prohibiting advertising a vehicle as being environmentally friendly, with large fines issued to violators.[27][28][29][30]

A study that looked at other factors other than energy consumption and carbon emissions has suggested that there is no such thing as an environmentally friendly car.[31]

The use of vehicles with increased fuel efficiency is usually considered positive in the short term but criticism of any hydrocarbon-based personal transport remains. The Jevons paradox suggests that energy efficiency programs are often counter-productive, even increasing energy consumption in the long run.[32] Many environmental researchers believe that sustainable transport may require a move away from hydrocarbon fuels and from our present automobile and highway paradigm.[33][34][35]

United States[edit]

The United States Environmental Protection Agency (EPA) is promoting the marketing of greener cars via the SmartWay program. The SmartWay and SmartWay Elite designation mean that a vehicle is a better environmental performer relative to other vehicles. This US EPA designation is arrived at by taking into account a vehicle's Air Pollution Score and Greenhouse Gas Score. Higher Air Pollution Scores indicate vehicles that emit lower amounts of pollutants that cause smog relative to other vehicles. Higher Greenhouse Gas Scores indicate vehicles that emit lower amounts of carbon dioxide and have improved fuel economy relative to other vehicles.

To earn the SmartWay designation, a vehicle must earn at least a 6 on the Air Pollution Score and at least a 6 on the Greenhouse Gas Score, but have a combined score of at least 13. SmartWay Elite is given to those vehicles that score 9 or better on both the Greenhouse Gas and Air Pollution Scores.

Progressive Insurance Automotive X Prize[edit]

The Progressive Insurance Automotive X PRIZE (PIAXP) is a set of competitions, programs and events, from the X PRIZE Foundation to "inspire a new generation of super-efficient vehicles that help break America's addiction to oil and stem the effects of climate change."[40]Progressive Insurance is the title sponsor of the prize, the centerpiece of which is the Competition Division, within which a $10 million purse will be divided between the winners of three competitions.

The essence of each competition is to design, build and race super-efficient vehicles that will achieve 100 MPGe (2.35 liter/100 kilometer) and can be produced for the mass market.[41] Within the Competition Division, there are two vehicle classes: Mainstream and Alternative. The mainstream class has a prize of $5 million. The alternate class has 2 separate prizes of $2.5 million, one for side-by-side seating and one for tandem seating.[42]

Some of the competitors, such as Aptera and Tesla, are already taking deposits for 'green' vehicles from customers.

Several automobile magazines, motor vehicle specialized publications and environmental groups publish annual rankings or listings of the best green cars of a given year. The following table presents a selection of the annual top pickings.